A stringed instrument such as a guitar has multiple strings supported in tension above a fingerboard. Each string is typically strung from the bridge at one end of the instrument, longitudinally across the fingerboard and over the “nut” at the end of the fingerboard opposite the bridge, and to a respective tuning peg, which can be rotated to adjust string tension. Tuning the instrument involves tensioning each string to a desired vibration frequency or “note”.
Strings are typically made of materials such as metal and nylon that can permanently elongate under tension, which is a process known as plastic deformation. New strings quickly go out of tune because they plastically deform or “stretch,” with a corresponding decrease in tension. Thus, it is common practice to vigorously “pre-stretch” a newly-installed set of strings by hand, to work-harden the strings and make them resistant to further elongation and de-tuning.
A string is properly pre-stretched by grasping it between the thumb and forefinger of each hand, with the hands spaced apart a short distance. One hand applies a force to the string in one direction across the fingerboard while the other hand simultaneously pulls the string in the opposite direction. The motion is repeated at multiple locations along the string to incrementally stretch the string across its entire length. This balanced “push-pull” technique coupled with a short hand spacing desirably minimizes lateral string displacement during stretching, as compared with simply pulling the string in one direction across or away from the fingerboard, which could damage the bridge or the nut groove in which the string is seated.
Strings are usually quite thin, and some can feel almost sharp to the touch. Although a regularly practicing musician develops sufficient finger calluses to comfortably withstand normal playing, it can be painful and tedious to pre-stretch strings with bare hands. Furthermore, pre-stretching by hand does not fully uniformly stretch the string along its entire length, because force is applied at a finite number of locations along each string. A string-stretching device is therefore desirable, to more uniformly stretch strings and to prevent the pain and discomfort of stretching by hand.
Few string-stretching devices are currently available on the market. One device currently marketed under the name PLANET WAVES™ is a multi-function peg-winder tool. The device includes a “string stretcher,” which, as best understood, is essentially a single arcuate recess incorporated into the handle for receiving a selected string. The user can pull on the string using the handle, rather than by grasping the string directly by hand. A drawback is the device only applies a force in one direction, and does not replicate the more effective push-pull method described above.
Another device with potential use as a string stretcher is disclosed in U.S. Pat. No. 6,107,556 to Gilliam. A string is threaded between a pair of string guides. The device is leveraged against the fingerboard of the guitar by pushing downward on a handle toward the fingerboard to pivot the device in a plane oriented perpendicularly to the fingerboard. This places the string in tension to pre-stretch the string and to facilitate winding of the string onto the tuning pegs. Although the Gilliam device may desirably impose a push-pull force on the string between the string guides, it has several drawbacks that make it non-ideal for use as a string stretcher:    (1) Because the strings are stretched in a vertical direction rather than a more desirable lateral direction, the strings are pulled drastically upward away from the fingerboard. Pulling up this far on a string can unseat the string from the nut. Undesirable upward forces may also be exerted against the bridge, which ordinarily secures the strings at the other end of the guitar.    (2) Potentially harmful downward forces are exerted on the fingerboard, which is often made of expensive woods and may have a delicate finish.    (3) The device requires an awkward balancing of its rather narrow edge against the fingerboard while being forcibly pivoted by one hand.    (4) While one hand operates the device, another hand must simultaneously operate the tuning pegs to wind the string. Winding a string onto a tuning peg, however, often requires two hands—one hand to turn the tuning peg and another hand to hold and guide the string very close to the tuning peg as it is wound. With two hands occupied at the tuning pegs, it may be nearly impossible for a single person to simultaneously operate the device.    (5) Because the device is leveraged against the fingerboard, it may be difficult or impossible to position the device to stretch the outermost strings, which are typically very close to the edge of the fingerboard. Because few string stretchers are available on the market, and because currently available devices are limited in their ability to properly stretch strings, an improved string stretcher is clearly desirable.
Because few string stretchers are available on the market, and because currently available devices are limited in their ability to properly stretch strings, an improved string stretcher is clearly desirable.